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The element also has 31 nuclear isomers, with masses of 141–154, 156, 158, 162, and 164–168 (not every mass number corresponds to only one isomer). [42] The most stable of them are terbium-156m, with a half-life of 24.4 hours, and terbium-156m2, with a half-life of 22.7 hours; this is longer than half-lives of most ground states of ...
The number of protons (Z column) and number of neutrons (N column). energy column The column labeled "energy" denotes the energy equivalent of the mass of a neutron minus the mass per nucleon of this nuclide (so all nuclides get a positive value) in MeV , formally: m n − m nuclide / A , where A = Z + N is the mass number.
The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number. For example, carbon-12 , carbon-13 , and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, and 14, respectively.
For other isotopes, the isotopic mass is usually within 0.1 u of the mass number. For example, 35 Cl (17 protons and 18 neutrons) has a mass number of 35 and an isotopic mass of 34.96885. [7] The difference of the actual isotopic mass minus the mass number of an atom is known as the mass excess, [8] which for 35 Cl is –0.03115.
The neutron number (symbol N) is the number of neutrons in a nuclide. Atomic number (proton number) plus neutron number equals mass number : Z + N = A . The difference between the neutron number and the atomic number is known as the neutron excess: D = N − Z = A − 2 Z .
The darker more stable isotope region departs from the line of protons (Z) = neutrons (N), as the element number Z becomes larger. This is a list of chemical elements by the stability of their isotopes. Of the first 82 elements in the periodic table, 80 have isotopes considered to be stable. [1] Overall, there are 251 known stable isotopes in ...
Most of the isotopes with atomic mass numbers below 14 decay to isotopes of carbon, while most of the isotopes with masses above 15 decay to isotopes of oxygen. The shortest-lived known isotope is nitrogen-10, with a half-life of 143(36) yoctoseconds, though the half-life of nitrogen-9 has not been measured exactly.
The helium hydride ion has six relatively stable isotopologues, that differ in the isotopes of the two elements, and hence in the total atomic mass number (A) and the total number of neutrons (N) in the two nuclei: [3 He 1 H] + or [3 HeH] + (A = 4, N = 1) [12] [13] [3 He 2 H] + or [3 HeD] + (A = 5, N = 2) [12] [13] [3 He 3 H] + or [3 HeT] + (A ...